It is often quite important to ensure that a web site or web application is secure from attack or perversion by hackers. In order to assist in this endeavor, network scanning tools exist which provide security management capabilities for network host computers or servers. One example of such a scanner is the Internet Scanner™ marketed by Internet Security Systems, Inc. of Atlanta, Ga., which product appears to be described in U.S. Pat. No. 5,892,903 to Klaus.
The shortcoming with network security products such as the Internet Scanner™ is that they only scan for vulnerabilities at the network level. The goal is to limit access to a web site to only designated protocols and services. To analogize, network-level security products can be thought of as a fence that forces access to the site only through a main gate, and network-level scanners seek to find the holes in the fence.
However, there also exists a need to ensure that a web site or web application is secure at the application level. Many web applications assume or depend that the application user is in fact executing a mobile agent of the application on the user's browser. However, a malicious user can overcome or modify the limitations or logic embedded in the mobile agent and send destructive or forged data to the web server. For example, one common type of web application is an online storefront wherein goods and services can be bought or sold over the Internet. A hacker should not be able to change the sale price of a product by manipulating the HTTP requests sent to the application program executing on a web server. A need therefore exists for an application-level scanner to identify application-level vulnerabilities. In other words, carrying on with the previous analogy, once the user is inside the gate it is important to identify ways in which the user may misbehave while on the premises.
Application level vulnerabilities have traditionally been discovered in a manner similar to looking for bugs in software—through a quality assurance or auditing process. Conventionally, this has been a completely manual process that can devour a significant amount of time. Not only does someone have to review the application line-by-line and understand the code intimately, they also have to try to imagine or anticipate potential security loopholes in the code. This is problematic in and of itself because many web developers lack the expertise and requisite knowledge to properly evaluate and correct application-level security flaws. This, coupled with the ever prevalent speed to market concern of getting new web applications on-line as fast as possible, makes human error in web development unavoidable. Worse yet, web applications are constantly changing and being upgraded while third party vendors are continually issuing patches that need to be implemented. In short, manual auditing processes to find application-level vulnerabilities are not very practical.